Warlow said: “Series three will start in 1894, and we’re going to have a look at the railways in the first episode. And there is something else which happened in 1894, the Macnaghten Memorandum.

"Melville Macnaghten was the assistant chief commissioner of the London Metropolitan Police who wrote an internal report that was for police eyes only, in which he named three suspects who he believed could have been Jack the Ripper.”

* Ripper Street will return to screens later this year on Amazon Prime Instant and next year on BBC One